Manufacture of articles from liquid dispersions



June19, 1945. I HABIB El AL 2,378,882

MANUFACTURE OF ARTICLES 1 30M LIQUID DISPERSIQNS I Filed Nov. 16, 19433nventors= AND GozwoNl'l GOTT Patented June 19, 1945 MANUFACTURE OFARTICLES FROM LIQUID DISPERSIONS Emile E. Habib and Gordon E. Gott,

Arlington,

Mass., assignors to Dewey and Almy Chemical Company, North Cambridge,Mass., a' corporation of Massachusetts Application November 16, 1943,Serial No. 510,443

4 Claims.

The present invention relates to the manufacture of meteorological,radiosonde, and emergency life-saving balloons, and more particularly toan improvement; in a dipping type process used in manufacturing thesearticles.

Balloons which are used to carry aloft weather recording instruments arequite large. The common sized balloon of this type is about three feetin diameter before ascension and expands during flight to 12 feet ormore. Because of this requirement, such balloons had, until the recentpast, been made by a casting procedure, as distinguished from a dippingprocedure. In this casting process a sensitized latex dispersion is castin a rotating, hollow, spherical mold im-' mersed in a hot water bath.The process is slow and, especially when used with chloro butadiene-1,3, the preferred material for certain military balloons, is toosensitive to slight variations in time and temperature, and consequentlyrequires too precise control for effective and economic factory use.This difficulty has, to a large extent, recently been over-come byintroduction of a dipping type process, in which the formed deposit isst iipped from the mold while it is still sufficiently soft from thepresence of water to be capable of plastic (as distinguished fromelastic) deformation, washed and then inflated while still plastic topermanently increase its size and make it more nearly spherical. Thisdipping process is described in detail in our co-pending application,Serial No.

510,442, filed on the same day as the present application. In practicingthis process on a factory scale, it was found that a substantialpercentage of the balloons burst during the inflation treatment beforereaching the desired size. Investigation showed that the uninflated gelof specimens which burst was of uniform auge over its entire area withinextremely close tolerance limits, so close that the failures duringinflation could not be accounted for on the basis of variations inwallthickness alone. Further investigation led to the discovery that anydroplets of water'remaining on the surfaces.

of the plastic gel from the washing following dipping were immediatelyabsorbed into the. material during inflation. It was then discovered.

from a study of the fragments of the burst specimens, that failure hadoccurred in those areas into which excess water had been absorbed. It isnot possible to avoid wetting the gels, because they must be washed toremove the coagulant which remains on their inner surface. It is notpossible to avoid local accumulations of water by drying the gels beforeinflation, because it is essential that the gels be still In accordancewith the present invention, the

percentage of failures in the manufacture of meteorological balloons bythe coagulant dipping process referred to above is substantially reducedby removing'any local accumulation of water from the surfaces oftheplastic gel which is to be stretched during inflation before theinflation step is carried out. The invention will be more fullyunderstood from a reference to th accompanying drawing, in which Figure1 is a sectional view of a dipping mold with the rubber deposit thereon;

Figure 2 is an elevation, partly broken away, of the stripped geldeposit;

tion on the inflation nozzle; and

Figure 4 is similar to Figure 3, but shows a later stage in theinflation step.

In practicing the present invention, a coagulant bath and a dipping bathof compounded rubber dispersion are made up according to establishedpractice in the dipping art. The following examples are illustrative ofsuitable coagulant and dipping compounds.

Example 1.For a meteorological balloon made from a polymerizedchloroprene-1,3 latex compound. I

A dipping compound is made up in accordance Figure 3 shows in sectionthe wet gel inposi V with the following formula:

Parts by weight I of solids 7 Polymerized chloroprene-1,3 dispersion-(neoprene type 571) 100.00 Dibutyl sebacate emulsion 15.00 NH: (asammonium hydroxide) 0.28 Hard clay (Suprex brand) 7.00

Dispersing agent (formaldehyde conden-' sation product of naphthalenesul- The dibutyl sebacate emulsion has the following formula:

. Parts by weight Zinc dibutyl dithiocarbamate The formula for thecasein solution is as follows:

Example 2.-For a life-saving (captive) The casein solution and;coagulant have the composition described in Example I.

Example 3.For a'balloon made from natural rubber latex; the dippingcompound has the following composition: r

' Parts by weight 0 of solids Rubber latex (60% solids) 100.00Potassiumhydroxide 1 1.75 Zinc stearate 1.00

Symmetrical 'di-beta naphthyl para phenamount will va with differentlatices. Suiiieient should be used to give e dispersion a viscositysuitable for dipping.

The ingredients are added in the order stated.

In manufacturing balloons by the preferred form of ,the present process,a conventional balloon mold II is dipped in the coagulant to form acoating -ll of coagulant on its surface. The coated mold is then dippedin the bath of rubber dispersion, allowed to dwell therein for the timenecessary .to build up a rubber gel deposit I! of the desired thickness,and then withdrawn and held for a short time in still air-at roomtemperature to .permit coagulant to diffuse throughout the depositedlayer i2 and complete coagulation of the very thin layer of mmlateddispersion which adheres to the outer surface of the coagulated gel I!as it is withdrawn as The excess water on the inside surface of theballoon which collects during inflation at the botover an'inflationnozzle l5, arranged in a ver-' tical position and having its orificefacing upwardly. A support forthe soft gel is provided adjacent theinflation nozzle; As shown in Figure,'3, the support takes the form of aring ll surrounding the nozzle oriiice and supp rted by arms .20 mountedat their lower ends on the nozale. Anyeircess liquid on, the outsidesurface of the balloon will flow downwardly onto the neck, and most ofit will drain away oi the end of the bal- 2g neck. Excess water -on theinside surface will hon hydrogen Parts by weight likewise draindownwardly and collect at It in' -Polymerized -chloroprene-l,3 dispe ionthe l a i t nozzle. Air under (neoprene type 571) 10090 a low pressureis then discharged through the 'Ammonia (as ammonium hydroxide) 0.2anozzle into e e si e it to expand. As it Hard clay (Suprex brand) 7.0025 ,expands, the rubber material undergoes plastic Dispersirig agent;formaldehyde-condensag z z g gmi n r a tlg flm :33 woduct naphthalenesulphonic 0J4 contract to its original size as would an ordinaryZinc'oxlde (Kadox) 5.00 W balloon- Phenyl'beta naphthylamine 2.00 sowhen 8 1 has been fully expanded, it is Casein'solution- (10%) 0.35 nthe x d condition which perms-- nently increases its size. The envelopesare then A I 114.77. deflated and may be subsequently vulcanized, if

desired, in air at 212 F.

. tom, will be in. contact with the gel only at its neck. The neck isstretched, much less severely ylene diamine 1.00 Formaldehyde"condensation product of naphthalene sulphonic acid. 0.24

Titanium dioxide 1.00

- Sulphur 1.10

duringthe inflation than is the body'portion; consequently excess waterat this point does no harm.

The inflation nozzle may be arranged, it desired, to permit the excesswater which drains from the inside surface of the balloon to flow outthe noule. For example, a trap may beprovided in the air line just belowthe nozzle.

The hivention may be practiced also by swabbing or wiping the excess.water from the surface of the gel before it is inflated, although wehave found this procedure to be less convenient than the methoddescribed above. The swabs or cloths used for wiping should preferablybe dusted with tale to prevent scufllng the gel.

It will be appreciated by those skilled in the art that the presentinvention is applicable to the manufacture or other dipped goods thanmeteorological and similar balloons. The process is applicable tothemanufacture of any object which lends itself to manufacture by thecoagulant dipping process of our application 8e No. 510,442, referredtoabove.

While the herein described process is particularly applicable tothepolymerized halogen butadiam-1,3 and natural rubber illustrated in theexamples, we believe it to be applicable to other elastomeric materialscapable of being made in speciflcationandintheclaimswehaveusedthc .wordrubber" in an inclusive sense.

We claim:

1. The method or making a hollow. rubber object having an opening whichcomprises dipping a coagulant-coated mold of smaller size than theobject into a liquid dispersion or rubber, withdrawing the mold from thedispersion with a layer of rubber gel thereomstripping the gel from themold while the gel is still plastic from the presv ence of water.removing free water from the surv face or the gel and enlarging theplastic gel to object into a liquid dispersionoi natural rubber,

withdrawing the mold from the dispersion with a layer 01' natural rubbergel thereon, stripping the gel from the mold while the gel is stillplastic the dispersion with a layer of polymerized chloro butadiene-l,3thereon, stripping the gel from the mold while the gel is still plasticfrom the presence of water, removing free .water from the surface of thegel, and enlarging the plastic gel to the desired size by inflating itwhile it is still plastic from the'presence of water interstitially'present in the gel, and thereafter drying the gel.

4. The method of making a hollow rubber object having an opening whichcomprises dipping acoagulant-coated mold of smaller size than the fromthe presence of water, removing free water from the surface of the gel,and enlarging the plastic gel to the desired size by inflating it whileit is stfll plastic from the presence of water interstitially present inthe gel, and thereafter drying the gel. 3. The method of making a hollowrubber object having an opening which comprises dipping acoagulant-coated mold of smaller size than the object into a liquiddispersion of polymerized chloro butadiene-1,3, withdrawing the moldfrom desired size 01' the finished object into a liquid dispersion ofrubber to deposit' a layer of rubber gel thereon, withdrawing the moldfrom the dispersion with the layer of gel thereon, stripping the gelfrom the mold while the gel is still plastic from the presence of water,and removing free water from the surface of the gel and enlarging thegel to the desired size by inflating it in inverted position with itsopening downward whileit is still plastic from the presence of waterinterstitially present in the gel, and thereafter drying the gel. EMILEE. HABIB.

GORDON E. GO'I'I'.

